CHAPTERIII

PHYSICALDEFENSESANDLIMITATIONS

Introduction

An effective base physical defense environment has as its goal four

objectives: the detection, detention, and destruction of the enemy; and,

of greatest importance, the preservation of vital resources while accom-I

plishing the preceding objectives.

This chapter briefly considers four aspects of physical defenses as

they existed in Thailand from 1968 to 1972. First, it examines active

defense systems designed to aid personnel in the detection, containment,

~, and response to an enemyintrusion. Then, the chapter details passive.

defense measuresdesigned to protect personnel and vital resources during

an attack. It explores the limitations imposed by natural conditions

as well as political and economic constraints on the use of defensive

devices. Finally, it briefly discusses someof the specific difficulties. .

and achievements. No effort is madeto duplicate concepts discussed in

PACAFM207-25.

f!f.1

'.-li

TwoCHECOreports on base defense concepts and measures in the

Republic of Vietnam provide aqditional information.123/

Active and Passive Defense ~easures

The first "ring of defensell within the bounds of USAFresponsibility

.was the base perimeter, usually composedof fence lines and other integrated

57

defenses, all designed to expose the enemyto an increased risk of obser-

vation and detection. No base considered itself secure because of an

impenetrable perimeter, for as one Chief of Security Police stated: "Fences

only keep honest people and cattle out, they don't stop determined sapper124/

squads."--:-

Perimeter lines at most bases consisted of various combinations of

chain-link fences. Somebases placed trip-flares amongthe fences. These

had wires which, when distrubed, would trigger the flare. (The figures on

the following pages illustrate some of the typical perimeter defense con-

cepts.) All bases (except Takhli RTAFB)had generally adequate lighting

on the perimeter fences and several had NF-2 Light-All units to provide

additional illumination as backup or in critical areas. Most of the bases

had Xenonlights with the capability of lighting several hundred meters with

either infrared or visible light; however, not a single base was able to

fully utilize' the~e units, either because of maintenance difficulties or

insufficient manning. Most installations also had various night observa-

tion devices (NODs)such as starlight scopes or the more expensive tower-

mounted NODs. Unfortunately, no base had sufficient numbers of these devices

to permit visual observation of the entire base perimeter. To further aid

in observation, herbicides were employed to assist in the difficult task. .

of vegetation control. Use of these agents ~as limited by such factors

as the ROEand supply problems.

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I

UNCLASSIFIED

.i

ill Bunker

~~ @ Tower

C> Field of Fire7-,?J<:J

? t M60 Nachine GunA2; 81MHMortar

'tf~ Mines

X~X Fe;')c€:Li ne~

;3-R; ~§ ~) Reserve/Unmanned Positions

Perimeter Defense System

FIGURE11

UNCLASSIFIED

I"I,1

UNCLASSIFIED

TAUT HORIZONTAL SUPPORTVIRE RACKED TO UPPER~ONCERTINA HALFWAYBETWEEN PIC;<ETS

~SECTION

TAUT HORIZONTALSUPPORT WIRE

ENEMY

Figure 3-1. Triple Standard Concertina Fence.

r

'"

PLANNOT'E:

E ES OF ALL PICKETS.POINTIN DIRECTIONFROM WHICHFENCE IS BEING ERECTED.

.Figure 3-2. Double Apron Fence.

ENEMY

Defensive Perimeter Fences

FIGURE12

UNCLA-SSIFIED

- -

/

'1

Only one base made use of any form of Tactical Security Support Equip-

ment. In January 1971, NakhonPhanomRTAFBwas the test base for the

Westinghouse AN/GSS-15Alarm Set. This system of intrusion detection used

the Balanced Pressure System (BPS). Test results were highly satisfactory.

FromJanuary 1971through June 1972, the system averaged 90 percent opera-

tional effectiveness. Future plans called for the late 1972 completion

of the NKPperimeter and the installation of equipment at U-Tapao, Ubon,12~

and Udorn RTAFB. The system at NakhonPhanomwas not really an inte-

grated part of the base defenses in mid-1972. The system covered about

30 percent of the base perimeter, but all of the sensory "actuators" or

alert lights were located in one observation tower. That tower had no

opportunity to observe all portions of the perimeter covered by the BPS.

Effective use would have required that each section of the perimeter be

under observation by a tower guard whowould be alerted by an alarm

triggered by any intrusion in his sector. Delay in communicating an

alarm from one tower to the sector guard in the area being penetrated'; 126/

would"have erfectfvely prevented detection.-

Great variations in perimeter defenses and detection devices were

~~ evident in 1972. PACAFM207-25 and periodic staff visits by 7/13AF

Security Police personnel provided the only commandguidance. Variations

in amount and types of fencing, use of trip-flares, tower height and

positioning, and circulation control procedures were in evidence from

base to base. Inner defenses also varied significantly, both from each12ij

other and from PACAFM207-25. No base had close-in defense perimeters

61

meeting the manual's standards, and none possessed intrusion detection

devices, such as trip-flares, around the vital resources. Further,

defensive fencing around such resources was generally incomplete or non-

existent, thereby limiting the site defenses to reliance upon humansentries

alone. Even this detection capability was hindered by inadequate lighting

around the perimeter of the close-in defenses; and aircraft noise also

served to complicate detection. This absence of in-depth site protection

was not due to any lack of perception by defense planners, but, rather,

was dictated by various practical considerations such as access to the

flight-line areas by maintenance personnel and equipment.

..f!'"~~

The second and third objectives of active defense were to contain

an enemyand respond.with adequate forces to destroy or repel him. Both

fencing and illumination were significant in providing this ability. Slap-

flares and 81mmmortars with illumination rounds were available at all

bases for use during any attempted or suspected penetration effort by

sappers. . .

Twosignificant deficiencies in base defenses existed throughout

Thailand and seriously limited the response capability of defense forces.

The first was a lack of adequate communications, and the second was vehicle

problems. Most bases had radios with only a two-channel capacity; while

adequate under normal conditi.ons, the urgency created by an emergency plus

. the difficulties of a multilingual defense force seriously overburdened128/

this system at times Further, maintenance problems and lack of

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sufficient quantities of vehicles, such as the armored personnel carriers

(APC/113and APC/706)and other rough terrain vehicles, madethem the number129/

one priority need of almost all bases.---

In addition to the foregoing, mines were another "responsell device.130/

The ROEprohibited IIClaymoreli mines in Thailand,- but in 1970 U.S.

Embassy permission was given for limited use of A/E 25P-l IIPOp-Uplimines. 131/

at all bases except Korat RTAFBand Don Muang Airfield, Bangkok These

command-detonated mines were not in use as of June 1972, but 400 were pro-

grammed as part of the defenses ofU-Tapao RTNAF,the Thai test base, for132/

1ate 1972.---

Response capability to a stand-off RAMattack was extremely limited.

The ROEprohibited employmentof USAFfirepower or aircraft in any suppression

rOle.133/ Only close coordination with RTGunits provided any form of active

defense. Howeve~,most bases did not have the capability to direct RTGunits. .

to a suspected launch site. Several bases possessed mechanical triangulation

devices knownas lIazimuth boardsll that enabled a fiarly accurate plot of RAM

element sources if two observers located the launch site and used the plotting

device correctly. Defense personnel, however, admitted that use of the board

was not practical and field exercises emphasizing its use were not conducted.

Further, except for NakhonPhanom'gHH-53 helicopter exercises, no serious

practice of close coordination with external RTGforces targeted to a simulated

RAMsite was undertaken. Failure to utilize these potentially effective134/

RAMcountermeasures was a result of the perceived "low" threat.-

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Passive defenses for RAMattacks, such as revetments for aircraft and

personnel shelters, differed widely. Aircraft dispersal, another effective

passive protection measure, was limited by the severe restrictions on

available ramp parking space. POLand MMSareas were likewise provided with

what few revetments and whatever dispersal space was possible under the

circumstances. Another example of the varied responses of defense planners

was "stand-off" fen"cing. Designed to shield defensive bunkers from an RPG

attack, this concept of defense initiated in early 1972 by 7/13AF SP had

yet to be fully implemented at base level by June. Indeed, several bases ~.

~

135/ ~had hardly begun the project.---

A series of reports from the bases to COMUSMACTHAIdetailed the multi-

million dollar impact of upgrading the physical defenses of USAF/Thaibases

since 1968. Also, the first attack caused defense planners to realize

that adequate base protection required muchmore than a few armed sentries136/

with rifles walking posts after dark behind a three strand barbed-wire fence.---

Howev-er",a ful'ly standardi zed base defense posture had not yet been attained

by mid-1972.

Limitations

Geographicconstraints provided manyproblems in the USAFbase defense

posture in Thailand. Contiguous population centers at many of the bases

severely limited opportunities for both observation and effective counterfire.

Further, tropical vegetation aided by-seasonal monsoonrains grew almost

faster than it could be controlled. Dense jungles were rated as the greatest137/

threat to the defenses at U-Tapao Other natural features such as streams

64

I

})!t~JJ

NAKHONPHANOMRTAFB1966

FIGURE13

i1"(

(;;J

,~i

'.

f..~,.,-:\.,

and drainage ditches, knownas "klongs," provided concealment and thus were

natural points of entry for enemysappers. Most bases relied on extra

illumination to counter the threat in those areas. The extent to which

vegetation has been cleared is graphically illustrated in the case of NKP.

The photograph of that base on the following page shows the extent of vege-

tation inside the base perimeters in the early days of construction when

the airfield was carved out of virgin jungle. An interesting comparison

betweenNKP1966and NKP1972can be madeby reference to the picture of

~ that base that appears earlier in this report. (See Figure 6.)

..,

Other constraints were imposedby various economicand political con-

siderations. There was a relative scarcity of resources and moneywhich

forced defense planners to establish priorities in the areas of the base

they were able to defend in depth. Thus POLand MMSareas had to compete

with aircraft, which past experience had shownwere more lucrative targets.

J" "'

_L~cal US~F~~~e commanders' emphasis on defense often varied. For

example, prior to the June 1972 attack, the base commanderof UbonRTAFB

directed that a triple concertina barrier be removed from an area between

aircraft revetments and the base perimeter, just 100 meters beyond. The

directive ordering the removal of the fence was part of a current IIbase

beautification" effort. This very area became the penetration point for the138/

sapper attack.- Occasionaily,.h;gher cOf1111andalso diverted defense

resources to areas with higher threat estimates. Barbed~tape, considered

the most effective anti-penetration barrier available for "use along

66

139/perimeters,--- was scheduled for installation at U-TapaoRTNAFin late 1971.

In November, PACAFdirected that the tape be held for possible diversion140/

to vulnerable Vietnam bases Four days after the January 1972 attack,

13AFdirected that the tape still at U-TapaoRTNAFbe employed in that base'sill!

defense. Thirteenth Air Force further indicated that the tape sent to142/

Vietnam would either be replaced or redirected back to U-Tapao.---

Construction projects, such as fence barriers, defensive bunkers, and 0~

observation towers, frequently had to await the completion of higher-priority~

civil engineering work orders. The response to this difficulty often was an ~

enormous SP self-help effort. Probably well over 50 percent of all defensive

structures in Thailand were constructed solely by security police personnel.

Higher headquarters, while commendingsuch vigorous efforts, cautioned

the field not to rely exclusively on self-help but to utilize regular Air143/

Force supply and civil engineering channels whenever possib1e.---

.....

-The U.S.<Emb.~~sy'sROEalso provided several limitations on physical

defenses. The original 1968 ROEprohibited the use of flareships. This

was changed in 1969, and flare drops and the use of 81mmmortars were approved

for illumination as long as the "trash" didn't impact outside the base.

Soil sterilization and herbicide use was also approved in 1969, but these

were subject to extensive coordination with local RTGauthorities and final

permission from the Embassy.. Th~y'could only be' used on areas within the

perimeter and under no circumstances could the vegetation control agents be144/

used to clear areas of observation to fire off-base This lengthy

67

I

process, and the inability to go beyond the fences, significantly limited145/

the use of those agents at many bases.---

The 1969 ROErequired advance approval of the Ambassador for all "new146/

weapons" introduced into Thailand This rule was used to limit the

previously-discussed, command-detonated pop-up mines. The Embassy limited

their installation to the launcher tubes. The actual mines and detonation

circuitry could not be installed until a "Yellow" (or higher) Security

Alert Condition was in effect. This stricture led CINCPACAFto cancel

.-}

the planned use of such mines when several efforts to secure fewer limita-147/

tions from the Embassyproved unsuccessful Finally, in May1972,

PACAFpermission was obtained to undertake a limited test of the mines

at U-Tapao, subject to the ROErestrictions. CINCPACAFthen requested

that Headquarters USAFseek greater freedom in their use and directed148/

that no further bases would be armed until the ROEwere modified.---

Base Analysis .

. Korat RTAFB.Vegetation control was a serious problemat this base

in 1972, especially in the critical RTAFarea near the end of the runway.

The dense growth offered opportunity for concealment in the area contiguous

to the unrevetted KC-l35 parking ramp. Further, vegetation was thick in

many sectors of the concerti~a wir: on the perimeter. The base had received

Embassy permission to use herbicides ~nd had just begun that program in

June.

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